Mushrooming Effects of Experience

After a few weeks spent working in the hive, worker bees become foragers that leave the hive to gather nectar and pollen. Foraging--which requires the abilities to navigate, remember the way back to the hive, differentiate among different types of flowers, and communicate information--is accompanied by an increase in the size of the mushroom bodies, brain regions implicated in certain forms of learning and memory. Ismail et al. marked honeybees of known age that had begun foraging and, after a week spent foraging, either allowed them to continue foraging for a second week or confined them to cages or hives. Mushroom body volume in bees that had spent a second week foraging was larger than that of bees that had been confined. There were no differences in the mushroom body volume between bees that had foraged for a single week and those that had been caged for the second week, indicating that foraging during the second week stimulated mushroom body growth. Caged bees that ingested the muscarinic agonist pilocarpine underwent an increase in mushroom body volume comparable to that of those that spent a second week foraging, an effect that was not seen in other brain regions and was blocked by the muscarinic antagonist scopolamine. Thus, the authors conclude that muscarinic signaling mediates an experience-dependent structural change in the bee brain and that bees may provide an amenable system in which to investigate cholinergic mechanisms involved in experience-dependent plasticity of brain structure.